There have been many variations of catheter apparatus. A typical torque transmitting catheter apparatus is illustrated by Cook, U.S. Pat. No. 3,924,632, which includes several different layers bonded together. Cook discloses a catheter having a core, surrounded by a reinforcing layer, which is in turn surrounded by a superstrate or covering layer. In previous catheters, such as R. C. Steven, U.S. Pat. No. 3,485,234, the reinforcing layer consists of metallic braid of wire filaments which generally has a round cross section. The instant invention comprises a multi-element catheter apparatus which includes a special thin walled reinforcing means and special structure for supporting the reinforcing means which minimizes mechanical failure, while reducing the overall outside diameter of the catheter apparatus and yet providing adequate flow rate characteristics.
Catheterization procedures are used to diagnose the condition of a patient's body tissue such as arterial passageways or the like. Normally, an incision is made in the patient's body in order to insert the catheter apparatus into the passageways to be diagnosed. The catheter is then inserted through the incision and into the desired passageway. The catheter is fed through the passageway until it is correctly positioned adjacent the desired body organ, such as the heart. The catheter is then precisely rotated and manipulated into the desired body organ, for instance, the right coronary artery. Diagnostic fluid is then injected into the passageway at a predetermined minimum flow rate in order for a separate device, such as an x-ray, to properly record in photograph form the passageway. The physician may then properly diagnose the patient's condition.
The above described insertion process can induce trauma to the walls of the patient's passageways. In order to minimize the trauma, the instant invention may have a small overall outside diameter.
Trauma is further minimized by providing a highly flexible catheter which bends in conformance with the passageways. However, the catheter must be rigid enough to provide adequate torque transmission. Without sufficient torque transmission, the catheter cannot be precisely rotated into the desired body organ. Further, poor torque transmission causes buckling, wind-up and whiplash, inducing trauma to the passageways and causing pain and discomfort to the patient. Thus, heretofore the medical profession has been faced with a trade-off between a highly flexible catheter apparatus which fails to function adequately in torsion or a rigid catheter which creates an intolerable amount of trauma. The instant invention solves this dilemma by providing a thin wall reinforcing means comprising a flat wire braid wound over a longitudinally pre-oriented substrate which adequately supports the reinforcing means. The braid is maintained in place by a surrounding superstrate. Using this structure, the instant invention has extremely good torque transmission characteristics while maintaining superior flexibility. And, while the Cook patent, supra, discloses a flat braid of fiber glass it requires bonding to minimize kinking.
Because the instant invention includes a pre-oriented substrate, extremely thin walls are possible. This allows the overall outside diameter to be minimized while maximizing the inside diameter. This allows adequate diagnostic fluid to flow though the substrate thereby enabling the x-ray machine or the like to properly photograph the desired passageway.
The instant invention comprises a pre-oriented thin walled substrate, a thin wall reinforcing means and a superstrate which together cooperate and interact in a manner different than previously known to produce a flexible, small diameter, torque transmitting catheter which has adequate fluid flow characteristics and which functions according to generally accepted medical standards, while minimizing pain and discomfort to the patient.